Stephen d



(No Model.)

S. D. FIELD. Speaking Telephone. No. 234,554. Patentgd Nov. 16,1880.

STEPHEN D. FIELD, QF NElV YORK, N. Y.

SPEAKING-TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 234,554, dated November 16, 188C".

Application filed June 4, 1880.

To all whom it may concern Be it known that I, STEPHEN D. FIELD, a citizen of the United States, residing in the city, county, and State of New York, have invented certain new and useful Improvements in Transmitters for Speaking-Telephones, of which the following is a specification.

My invention relates to that class of speaking-telephones in which a continuous current from a battery or other source of electricity is thrown into undulations, waves, or vibrations by the action of a sonorous body, usually a plate or membrane, which body is so arranged as to produce, by means of its movements under the influence of sound-waves, a variation in the resistance of the circuit through which thecontinuouscurrcntflows. Thesevariations of resistance cause a OOITCSPODClll'lg rise and fall in the effective strength of the said current throughout the circuit, which is made to produce corresponding mechanical movements at the receiving-station, whereby the atmosphere is thrown into vibration at that point and the original sounds reproduced.

To this end my invention consists, first, in the combination of a resonant plate or membrane having acondncting-electrode rigidly at tached thereto, and a second electrode normally maintained in contact with the first one by a constant force, with means for maintaining a continuous supply of heated products of combustion, and a tube for directing the same upon or between the said electrodes 5 second, in a movable electrode mounted upon a swinging arm, which arm is carried by friction from a constant motor, and tends to maintain said electrode in contact with a vibrating electrode.

In the accompanying drawings, Figure 1 represents a side elevation, partly in section, of myimproved transmitter. Fig.2 is adetached sectional view of a portion of the apparatus shown in, Fig. 1.

In the figures, A is a circular case or frame made in two parts, within which is formed a chamber, a. This chamber incloses a plate, disk, or membrane, B, clamped at its edges, but with its central portion left free to vibrate responsively to sound-waves which are concentrated and thrown upon it through the conical mouth-piece 0.

To the center of the plate B is rigidly at- (No model.)

tached a rod or needle, I), which is armed at its extremity with a metallic point or button, D, preferably faced with platinum.

The case A is attached to the outside of a vertical cylindrical tube, E, which tube constitutes a chimney for conveying away the heated products of combustion from the flame f of the lamp F. This lamp is mounted upon a suitable base, G, which also carries a standard, H.

From the top of the standard H projects a horizontal steel pin, h, which forms an axle for the pulley I, which turns loosely upon it, and may be caused torevolve in the direction of the arrow by turning the large pulley J by means of the crank K, the motion being communicated to the pulley l by means of a band or cord, t. Upon the pin h, which serves as an axis for the pulley l, is also placed loosely a wheel, L, (see Fig. 2,) which tends to revolve by the friction of the pulley I, a disk of leather or thick cloth, Z, being interposed between them, and a slight or constant pressure being applied to the adjacent surfaces by means of a spiral spring, M, confined by a screw, m.

The wheel L carries a curved swinging arm, N, upon the extremity of which is fixed a metallic button or point, 0, preferably faced with. platinum. This is so placed and adjusted that when the crank K and its attachments are steadily rotated in the direction indicated by the arrows the button 0 will be forced with a constant but very slight pressure into contact with the button I). The pressure will be determined both by the strength of the spring M and the rapidity with which the pulley I is made to revolve.

screw 5, whence the wire 6 extends to the re-- ceiving-station.

The flame f of the lamp F is to be so adjusted as to impinge directly upon the buttons D and O, and when they are separated to pass directly between them, the object of which arrangement will be hereinafter set forth.

The operation of the apparatus is as follows: The lamp F, being supplied with suitable combustible material, mineral hydrocarbon oil by. preference, is lighted, and the heated products of combustion arising from the flame f are directed upon and between the electrodes. Matters being in this condition, and a constant current of electricity from the battery P traversing the line, the operator at the transmitting-station proceeds to turn the crank K in the direction of the arrow, and at the same time speaks into the mouth piece 0. This causes the plate B to vibrate in response to the acoustic vibrations set up in the atmos phere by the voice of the speaker, and the needle I) and its attached electrode D necessarily partake of the movement and advance toward and recede from the electrode 0, the action being such as to produce a space of varying width between the electrodes corresponding to the action of the soundwaves. The flamef, com posed of heated products of combustion, passing between the electrodes, being a partial conductor, serves to bridge over the space between them and permit the current to pass without interruption from one electrode to the other, while at the same time its resistance varies greatly, according to the distance between the electrodes. Thus the heated products of combustion of which the flame f is composed constitute, in effect, a variable resistance,

which is controlled by the movements of the plate B, in the manner hereinbefore explained.

At the receiving-station the constant current, which has been thrown into electric waves or vibrations by the method and apparatus hereinbefore described, is made to pass through a telephone receiving-instrument of any wellknown or suitable character.

Where the line is of great length it will be found preferable to place the instrument in the primary circuit of a suitable inductioncoil, and connect the secondary circuit of the coil with the line-wire extending to the distant or receiving station, in a manner well understood.

1 claim as my invention 1. The combination, substantially as specified, of a resonant plate or membrane having a conductirig-electrode rigidly attached thereto, and asecond electrode normallymaintained in contact with the first one by a constant force, with a lamp or other device for maintaining a continuous supply of the heated products of combustion, and a tube for directing the same upon or between the said electrodes.

2. A movable electrode mounted upon a swinging arm carried by friction from a constant motor, which tends to maintain said electrode in constant contact with avibrating elec trode, substantially as set forth.

Signed by me this 3d day of June, A. D. 1880.

Witnesses: STEPHEN D. FIELD.

FRANK L. POPE, MILLER G. EARL. 

